The present invention relates to a manufacturing method of high concentration ozone gas and an apparatus thereof using a pressure swing adsorption apparatus (PSA apparatus) having plural adsorbing layers filled with a specific high silica ozone adsorbent large in the difference of ozone adsorbing amount between adsorption pressure and desorption pressure, that is, the ozone adsorbing capability.
The invention also relates to a manufacturing method of high concentration ozone gas and an apparatus thereof for concentrating ozone by a temperature swing adsorption system for changing over an ozone adsorbing process at a relatively low temperature and an ozone recovery process at a relatively high temperature, by using a specific ozone adsorbent having a high ozone adsorbing capability even in the presence of water.
Ozone is produced by using silent discharge apparatus or water electrolytic apparatus, but the ozone gas obtained from these apparatuses are low in concentration, and it is usually used after concentrating by an ozone adsorbing apparatus or the like.
As an ozone concentrating apparatus, an oxygen recycling ozone generating apparatus using liquid oxygen is proposed (Japanese Patent Application Laid-open No. 53-64690). A schematic diagram of this apparatus is shown in FIG. 15. It is a feature of this apparatus that liquid oxygen is used as the oxygen material. This liquid oxygen 31 is fed into an ozone generating apparatus 32, and the gas containing the ozone is cooled to about -60.degree. C. by a heat exchanger 33 and a refrigerating machine 34, it is further fed into an ozone adsorbing tower 35 filled with silica gel to adsorb ozone, the gas containing oxygen flowing out from the adsorbing tower 35 is fed into the heat exchanger 33 to cool the gas containing the ozone, and it is returned to the material side of the ozone generating apparatus 32. On the other hand, the adsorbing tower 35 having adsorbed the ozone is transferred to the desorbing process, and the air 37 dried by a dryer 36 is heated by a heat exchanger 38, and is fed into the ozone adsorbing tower 35 to be heated, purged and desorbed, and a concentrated ozone gas 37 is recovered, while the desorbed concentrated ozone gas 39 is fed into the heat exchanger 38, and the dried air is heated. Consequently, the regenerated adsorbing tower 35 by desorbing the ozone is transferred from the desorbing process to the adsorbing process.
Thus, the silica gel is known as ozone adsorbent, but since it is extremely large in the moisture adsorbing capability as compared with ozone, if moisture is present in the gas contacting with the adsorbent (the gas to be treated, purge gas, and the like), the moisture is preferentially adsorbed by the silica gel, and it is hard to desorb the once adsorbed moisture, and the moisture is accumulated, and hence it is difficult to maintain a specific ozone adsorbing capability. As a result, an extremely large amount of silica gel is needed for maintaining a specific gas treating capacity, and the adsorbing apparatus itself is increased in its size. Besides, when adsorption and desorption of moisture are repeated, the silica gel is powdered and may be lowered in the adsorbing capability.
In the aforesaid apparatus, using liquid oxygen as oxygen material, by preliminarily drying the purge gas and feeding into the adsorbing tower, moisture is prevented from mixing into the adsorbing tower filled with silica gel, and the ozone adsorbing amount is increased by utilizing the low temperature of the liquid oxygen.
Generally, the ozone adsorbing amount is larger as the temperature is lower, but it is hard to cool lower than -60.degree. C. unless a particular refrigerating machine is used, and a large amount of adsorbent is usually required for increasing the treated gas amount, and the apparatus becomes larger in size, which causes to increase the manufacturing cost and running cost of the apparatus.